Presensitised planographic printing plates and methods of preparing and using such



aired States Patent 3,220,832 PRESENSITISEEB PLANOGRAPHIC PRINTINGPLATES AND METHODS OF PREPARING AND UdiNG SUCH Fritz Uhiig,Wiesbaden-Biebrich, Germany, assignor, by mesne assignments, to AzoplateCorporation, Murray Hiil, N].

No Drawing. Filed July 18, 1961, Ser. No. 124,804 Claims priority,application Germany, Aug. 5, 1960, K 41,387; Feb. 25, 1961, K 43,011 38Claims. (Cl. 96-4) This invention relates to plates for planographicprinting, wherein aluminum is used as a supporting material for thereproduction coating and is provided with a thin coating consisting ofone or more phosphonic acids and/ or derivatives thereof.

Aluminum that is to be used as supporting material for the preparationof planographic printing plates requires a preliminary treatment toenable the reproduction coating to adhere well. Virgin aluminum sheethas been processed mechanically, by means of graining machines, or steelor plastic brushes, to give a suitable supporting material.Light-sensitive coatings do not, however, adhere to material treated inthis way to the extent that is desirable, if very long printing runs areto be obtained. The aluminum surface has also been first cleaned withalkaline agents, possibly then etched with nitric acid, and finallysilicated by treatment with aqueous alkali silicate solutions. Aluminumtreated in this way has the disadvantage that only a very few types oflight-sensitive coatings, all negative-working, adhere thereto.

Aluminum has also been treated electrolytically for reproductionpurposes. This process is, however, very troublesome, particularly withregard to current supply in the case of the processing of a continuousband of material, and Where wide bands of aluminum are being treated.

Planographic printing plates comprising an aluminum support and areproduction coating adherent thereto have now been found in which thereis a thin intermediate layer between the aluminum support and thereproduction coating, the thin intermediate layer consisting wholly orin part of at least one phosphonic acid and/ or derivative thereof.

For the preparation of the planographic printing plates of theinvention, aluminum plates which have a phosphonic acid coating arecoated with a reproduction coating, preferably dissolved in a solvent,by known methods, e.g., immersion, roller application, application tothe support while rotating, and the like. The solvent is then removedand aluminum supports covered with an even, homogeneous coating arethereby obtained which can be converted by known methods into platesready for printing.

The phosphonic acid coating is produced on ordinary commercial gradealuminum, particularly in the form of plates or, with continuousprocessing, in the form of continuous bands, in accordance with knownmethods for the production of coatings. The aluminum may be subjected,before the phosphonization process, to one of the known cleaningprocesses, e.g., in hot alkali phosphate or carbonate solution, inoxidizing agents such as dilute nitric acid, or in nitrate, chromate orhydrogen peroxide soluice tions. The aluminum may also be cleaned by theaid of electric current, either cathodically or anodically.

The aluminum can then be immersed in cold or hot solutions of phosphonicacids, or derivatives or substitution products thereof, in water or ininorganic or organic solvents. A phosphonic acid coating may also beformed by roller application or by the application of phosphonic acidsolutions to the supporting material while rotating.

The phosphonic acids used in the present invention include organicphosphonic acids and derivatives thereof in the broadest possible sense,including aromatic, substituted aromatic, substituted andnon-substituted saturated and unsaturated cyclic, aliphatic,heterocyclic phosphoric acids and also polymers and interpolymers ofunsaturated phosphonic acids with each other or with other vinylcompounds, as well as derivatives thereof, such as salts or esters.

The following may be mentioned by way of example: vinyl phosphonic acid,polyvinyl phosphonic acid, 2-phosphono-ethane-l-sulfonic acid, vinylphosphonic acid monomethyl ester, vinyl phosphonic acid ethyl ester, 4-chlorophenyl phosphonic acid, 4-chloro-3-nitrophenyl phosphonic acid,S-nitronaphthalene phosphonic acid, B-styryl phosphonic acid andinterpolymers of vinyl phosphonic acid with acrylic acid and vinylacetate or mixtures thereof and their salts. Depending upon the natureof the aluminum surface, the temperature employed and the concentrationof the phosphonic acid solution, the treatment requires from a fewseconds to several minutes. In general, treatments of 5 seconds to 10minutes, preferably 60 seconds to 2 minutes, at temperatures of 20100 C.with about 0.001 to 10% (preferably 0.01-3%) solutions of phosphonicacids are adequate. The treatment may be further prolonged and eitherhigher or lower concentrations may be used if desired. However,conditions outside the range mentioned may often either be lessfavorable or not produce any improvement in results. If the aluminumplates are immersed in a bath, the bath may contain 0.1% phosphonic acidsolutions in water or organic solvents, for example; if the coating isto be applied to the support, while rotating, 0.011% phosphonic acidsolutions in organic solvents such as methyl ethyl ketone, toluene,butyl acetate, ethylene glycol monomethyl ether or dimtehyl formamide ormixtures thereof are preferably used.

Suitable compounds to improve the hydrophilic properties of the aluminumsurface, such as hydrophilic colloids, e.g., cellulose others such ascarboxymethyl cellulose, hydroxyethyl cellulose and methyl cellulose oralginates, may be added to the phosphonic acid solutions.

The resultant phosphonic acid coating may be briefly rinsed with waterand then dried. Drying at fairly high temperatures has an advantageouseffect on the adhesion of the coatings. Solutions of the organicreproduction coatings can then be coated by hand or by means of suitablecoating machines.

The materials used for the reproduction coatings for the plangrophicprinting plates of the present invention are, in general, any withwhich, as a result of the action of visible, ultra-violet or infra-redlight or X-rays or heated objects, image-wise differentiation ispossible, e.g., light-sensitive organic compounds such as aliphatic andaromatic esters, hydrazides and amides of naphthoquinone-diazidesulfonic acids, cinnamal malonic acid, its substitution productsandfunctional derivatives, diazonium salts of amino-diphenylamine andcondensation products thereof with formaldehyde, ortho and para-quinonediazides of benzene, anthracene and heterocyclic systems, e.g., ofquinoline, indazole, benzimidazole, fluorene and diphenylene oxide, alsodiazo ketones, unsaturated ketones, ortho and para-iminoquinonediazides, derivatives of alkyl-nitronaphthalene sulfonic acids,nitroaldehydes, acenaphthenes, nitrous, stilbenes, azides and diazidesand higher-polymeric diazo compounds.

A particularly suitable light-sensitive substance is a condensationproduct free of metal salts and obtained by acid condenation of adiphenylamine-4-diazonium salt with formaldehyde. When a light-sensitivesubstance of this kind is employed, the copying material is highly lightsensitive, has very good shelf-life and is very resistant to rubbing.

Example of suitable polyfunctional diazonium salt free of metal salt arethose obtained by condensation of the diazonium salt, e.g.diphenylamine-4-diazonium chloride, diphenylamine-4-diazonium bromide ordiphenylamine-4- diazonium phosphate, with formaldehyde in strongphosphoric acid or polyphosphoric acid. The crude condensate may bediluted and then applied direct to aluminium which has been pretreatedwith a phosphoric acid and dried. However, after the completion ofcondensation, the phosphoric acid may be separated from the reactionmixture in the form of a feebly soluble salt by treatment with asuitable metal carbonate, bicarbonate or hydroxide, and the readilysoluble neutral halide of the condensation product may be isolated insolid form by evaporation. It is not essential for phosphoric acid to beused as condensation agent; the condensation product can also beobtained by condensation of an unsubstituted or substituteddiphenylamine-4-diazonium halide with formaldehyde in hydrofluoric acid,hydrochloric acid or hydrobromic acid and recovering the condensationproduct by evaporation in vacuo.

Also, reproduction coatings can be applied which have a high electricalresistance in the absence of light but which decreases by several powersof ten under the influence of light or heat, such as are used inelectrophotography and electrothermography, e.g., organicphotoconductors of lower or high molecular weight, if desired inassociation with resins. Photoconductors that have proved particularlysuitable are oxadiazoles, imidazolones, triazoles, oxazoles, thiazoles,hydrazones, triazines, polyvinyl carbazole and polyvinyl oxazoles.

As the resins, those which are suitable have groups conferringalkali-solubility such as acid anhydride, carboxylic acid, sulfonicacid, sulfonamide or sulfonimide groups e.g., vinyl polymers and vinylinterpolymers, phthalic acid ester resins, maleinate resins, alkydresins, colophony resins and polyacrylic acid resins.

The planographic printing plates of the invention have the advantagethat practically all known types of reproduction coatings adhereexcellently to the phosphonic acid surface and, moreover, after theusual image-wise exposure and removal of the coating in the image-freeparts (which may be eflfected with water, weak alkalis or acids,according to the type of reproduction coating used), they give longprinting runs in the machines normally used for offset printing,sometimes several times the length of those obtained with grainedaluminum foils such as have hitherto been used. The planographicprinting plates have the further advantage that they are very easy toprepare, as ordinary rolled aluminum sheet can generally be passedimmediately to a bath and subjected to the phosphonic acid treatment.

The invention will be further illustrated by reference to the followingspecific examples:

Example I A mechanically roughened aluminum foil is immersed for 60seconds at C. in a bath of 0.01% polyvinyl phosphonic acid in solutionin pure water. After being dried, it is coated with a 1% aqueoussolution of the zinc chloride double salt of a diazo compound preparedby condensation in sulfuric acid of 1 mole of 4-diazodiphenylamine and 1mole of formaldehyde. After exposure under a master, the diazo compoundis dissolved away, in the parts not affected by the light, by rinsingwith water and the image parts are inked up with greasy ink. Printingcan then be performed in the usual way. This diazo compound does notadhere satisfactorily to mechanically roughened aluminum surface thathas not had a preliminary phosphonic acid treatment.

Example I! A thin band of virgin aluminum sheet is drawn through a bathcontaining a hot C.) solution of 0.1% vinyl phosphonic acid and 0.01%carboxymethyl cellulose in Water. It is then dried, coated with a 2%solution of l-(4-methylbenzene-l-sulfonyl) imino 2(2,5"-dimethyl-phenylamino sulfonyl) benzoquinone (1,4)- diazide-(4) inethylene glycol monomethyl ether in known manner, dried again and cutinto suitable sheets.

For the preparation of a printing plate, the coated side of the foil isexposed under a film master and the exposed coating is treated with acotton pad that has been soaked in 3% trisodium phosphate solution. Inthe parts affected by the light, a yellow image of the master is leftadhering. After it has been rinsed down with water, it is inked up withgreasy ink and can be used for printing in a conventional machine.

This diazo compound does not adhere satisfactorily to virgin aluminumplate that has not had a preliminary phosphonic acid treatment.

Example III An aluminum foil is coated on a rotating whirler with a 1%solution of S-nitronaphthalene phosphonic acid in ethylene glycolmonomethyl ether, dried and then coated, by the method described abovewith a 1.5% solution of 4-diazodiphenylamine chloride and dried.

After exposure under a master, an image that is negative in relation tothe master is obtained if the parts unaffected by the light aredissolved away with water. After the plate has been inked up with greasyink it can be used for printing. In the image parts the coating isresistant to rubbing with 20% phosphoric acid while on aluminum that hasnot been given a preliminary treatment with phosphonic acids this diazocompound has only poor .adhesive properties.Z-phosphonoethane-l-sulfonic acid, vinyl phosponic acid monomethyl esteror vinyl phosphonic acid monoethyl ester can be used with equal successinstead of 5-nitro-naphthalene-phosphonic acid.

Example IV On a rotating whirler, an aluminum foil is coated with asolution of 0.05% vinyl phosphonic acid and 0.05% polyvinyl phosphonicacid in ethylene glycol monoethyl ether, dried, coated by the methoddescribed above with a 1.5% solution of thenaphthoquinone-(1,2)-diazide-(2)- S-sulfonic acid ester of2,3,4-trihydroxybenzophenone in ethylene glycol monoethyl ether anddried with hot air.

After exposure with a diapositive, an image which is positive withrespect to the master is obtained if the coating is dissolved away, inthe parts affected by the light, by wiping over with a cotton pad thathas been soaked in 3% trisodium phosphate solution. The plate is rinsedwith water and phosphoric acid of about 1% concentration and the imageparts are inked up with greasy ink.

Example V A mechanically roughened aluminum foil is immersed for 5minutes at 70 C. in a 20% aqueous solution of trisodium phosphate andthen for 60 seconds at 20 C. in a bath of 0.1% aqueous polyvinylphosphonic acid. After this layer has been dried, it is coated with asolution, in ethylene glycol monomethyl ether, of 0.3% of-2-phenylimino3 hydroxyethyl-5-cinnamylidene-thiazolidon-(4), 0.3% of di-cinnamylideneacetone and 0.3% of a phenol resin modified by reaction withchloroacetic acid. After exposure under a photographic negative, thelight-sensitive coating is hardened in the parts affected by the lightand dissolved away in the parts not atfected by the light by wiping overwith a solution of 50 parts by weight of sodium metasilicate in 700parts by volume of water, 500 parts by weight of triethylene glycol and200 parts by weight of glycerine. The image parts are then inked up withgreasy ink.

Example VI 1 part by weight of 2,5-bis-[4-diethylaminophenyl-(1)]-1,3,4-oxadiazole, 0.8 part by weight of a styrene interpolymer,containing carboxyl groups and having a specific gravity of 1.26-1.28and a decomposition temperature ranging from 200 to 240 C., and 0.003part by weight of Rhodamine B extra (Schultz, Farbstofrtabellen, 7thedition, vol. 1, No. 864) are dissolved in 30 parts by volume ofethylene glycol monomethyl ether. The solution is coated upon analuminum foil which has been treated for the production of a phosphonicacid coating, as described in Example I, and then dried. For theproduction of images on the electrocopying material thus prepared, thecoating is charged by means of a corona discharge and then exposed undera master for one second to a l25-watt mercury lamp. The resultantelectrostatic image of the master is made visible by dusting over with aresin powder pigmented with carbon black and fixed as an irremoveableelectrocopy by heating to 150 C. For the preparation of a printingplate, the electrocopy is wiped over with a solution consisting of 30parts by volume of methanol, 20 parts by volume of glycerine and 35parts by volume of ethylene glycol monomethylether. The plate is thenbriefiy rinsed with water and treated with dilute (about 0.5 to 5%)aqueous phosphoric acid solution. After the resulting printing plate hasbeen inked up with greasy ink, it can be used for printing in the usualmanner in an offset machine, direct images corresponding to the masterbeing obtained.

Example VII A mechanically roughened aluminum foil is immersed for 60seconds at 30 C. in a solution in water of 0.8% of polyvinyl phosphonicacid and 0.2% of vinyl phosphonic acid. After the aluminum foil has beenrinsed with water and dried, the foil is coated with a light sensitivesolution containing 0.5 part by weight of a crude condensate ofparaformaldehyde and diphenylamine-4-diazonium chloride described indetail below, 8 parts by weight of water, 80 parts by weight of glycolmonomethyl ether and 20 parts by weight of dimethyl formamide. Thecoated aluminum foil is dried and heated for a further two minutes to100 C. The light sensitive coating, which has very good keepingqualities in the unexposed state, is exposed with a photographicnegative, e.g., for 40 seconds to an lS-amp arc lamp at a distance of 70cm. The exposed coating is developed with an aqueous solution containing8% of gum arabic by means of a pad and is then inked up with greasy ink.The plate is then ready for printing. The image on the printing platemay also be strengthened with lacquer in known manner. Alternativelydevelopment and lacquering can be effected simultaneously by means of anaqueous emulsion lacquer. The resulting printing plate isextraordinarily resistant to rubbing with phosphoric acid and with thephosphoric acid anti-scumming agents commonly used in printing machines.

The support used can also be an aluminum foil covered with a layer ofBohmit, an electrolytically roughened aluminum foil or a foil of virginaluminum sheet. The results obtained are just as good as those obtainedwith the mechanically roughened aluminum foil.

The crude condensate from paraformaldehyde and diphenyl-4-diazoniumchloride is prepared as follows:

3.3 parts by weight of paraformaldehyde and 23 parts by weight ofdiphenylamine-4-diazonium chloride are stirred at room temperature into42 parts by weight of 85% phosphoric acid. A viscous solution is formedwhich is further stirred for half an hour at room temperature and thenheated to 40 C. This temperature is maintained for a further 24 hoursand the reaction is then completed. If desired, the phosphoric acid canbe replaced by the same quantity of pyrophosphoric acid ormetaphosphoric acid.

The condensation producta thick homogeneous mixturehas excellent keepingqualities which even allow it to be consigned for transport. It can bemixed with water and with many organic solvents, e.g., methanol or otheraliphatic alcohols, dioxane, ethyleneglycol monomethylether, anddimethyl formamide. Thus, it is possible for the coating solution to beadapted so far as concerns the solvent to the material which is to becoated. The condensation product may also be used in admixture withwater-soluble additives or with additives which are not soluble in waterbut are soluble in organic solvents. For many purposes the viscousreaction product can be used direct and without isolation which is veryadvantageous.

In the same manner, and with equally good results, one of the followingcompounds may be used instead of the diphenylamine-4-diazonium chloridefor the condensation with formaldehyde in phosphoric acid:

3-methoxy-diphenylamine-4-diazonium chloride,2-methoxy-diphenylamine-4-diazonium chloride,3-methyl-diphenylamine-4-diazonium chloride,4'-methoxy-diphenylamine-4-diazonium chloride,3-ethoxydiphenylamine-4-diazonium chloride,

The condensation products are prepared in analogy to the preparation ofthe unsubstituted condensate described above.

Example VIII A presensitized printing foil is prepared as described inExample VII but the sensitizing solution contains, in addition to 1.25percent of the condensate described in Example VII, 0.75 percent of aninterpolymer containing carboxyl groups (85% vinyl chloride, 14% vinylacetate, 1% maleic acid).

Example IX The procedure described in Example VII is followed, but thesensitizing mixture contains, as the light sensitive substance, a crudecondensate prepared in accordance with Example VII but using for thecondensation an equivalent quantity by weight ofdiphenylamine-4-diazonium bromide or diphenylamine-4-diazonium phosphateinstead of diphenylamine-4-diazonium chloride.

Example X A 1 percent aqueous solution of polyvinyl phosphonic acid isapplied by means of a cotton-wool pad to a paper sheet to which a thinaluminum foil is laminate. The foil is dried and then treated with a 2.5percent aqueous solution of the condensation product described inExample VII. The light sensitive coating, which keeps well in theunexposed state, is exposed with a master and converted into aserviceable printing plate, preferably by wiping over with a cotton woolpad soaked in water.

Example XI An aluminum foil is coated in a rotating whirler With asolution consisting of 0.1 part by weight of polyvinyl phosphonic acid,10 parts by weight of water, parts by weight of ethyleneglycolmonomethyl ether, and 20 parts by weight of dimethyl formamide. Afterdrying, the pretreated aluminum foil is coated with a solutioncontaining 0.1 part by weight of a condensation product prepared fromdiphenylamine-4-diazonium phosphate and formaldehyde in phosphoric acidand precipitated in the form of an acid phosphate in a mixture made upof 18 parts by volume of 2.5 percent (by weight) phosphoric acid, 160parts by volume of water, 1080 parts by volume of ethyleneglycolmonomethyl ether, and 720 parts by volume of dimethyl formamide. Thefoil is then dried.

The light sensitive coating, which has excellent keeping qualities inthe unexposed state, is exposed with a photographic negative andconverted into a printing plate, advantageously by wiping over with 0.5percent aqueous phosphoric acid. The printing plate is very serviceableand is very resistant during printing to the usual phosphoric acidanti-scumrning agents.

The acid phosphate of the condensation product fromdiphenylamine-4-diazonium phosphate and formaldehyde used for thepreparation of the coating solution is prepared as follows:

5.63 parts by weight of paraformaldehyde are condensed in 42.6 parts byvolume of 85 percent phosphoric acid with 50 parts by weight ofdiphenylamine-4-diazonium phosphate for 24 hours, at 40 C. 50 parts byweight of the crude condensation mixture are diluted with 125 parts byvolume of methanol and the resultant solution, heated to 40 C., isstirred in a thin stream into 500 parts by volume of isopropanol whichis kept vigorously agitated. The fine precipitate is stirred for 10minutes at room temperature and then further stirred at 30-35 C. untilthe original precipitate has changed into a sandy, quickly settlingpowder. This is filtered off, suspended in 100 parts by volume of freshisopropanol, again filtered off, washed with isopropanol and dried at30-40 C.

The diphenylamine-4-diazonium phosphate may be prepared as follows: Asolution of 1100 parts by weight of Na I-IPO .12H O and 40 parts byvolume of 85 percent phosphoric acid in 6000 parts by volume ofdistilled water is heated to 70 C. and poured into a solution of 500parts by weight of diphenylaminel-diazonium chloride in 1000 parts byvolume of 85 percent phosphoric acid, with thorough stirring. Thediazonium phosphate precipitates out in orange-colored crystals. Thereaction mixture is cooled to 20 C. and the diazonium phosphate isfiltered off. It is washed four times with 500 parts by volume ofdistilled water, once with 500 parts by volume of ethanol, and twicewith 500 parts by volume of isopropyl ether, and then dried in the air.560 parts by weight are obtained of chloride-free diphenylamine-4-diazonium phosphate of the composition C H NHC H N H PO Example XII Afoil of virgin aluminum sheet is immersed for 120 seconds at 85 C. inwater containing 1 percent of polyvinyl phosphonic acid and 1 percent ofvinyl phosphonic acid. After the aluminum foil has been rinsed down withwater and dried, it is coated with a solution consisting of 0.14 part byweight of a condensation product prepared from diphenylamine-4-diazoniumchloride and formaldehyde in hydrochloric acid and separated in the formof the chloride, and 0.13 part by weight of 85 percent phosphoric acidin a mixture of 8 parts by volume of water, 55 parts by volume ofethyleneglycol monomethylether, and 37 parts by volume of dimethylformamide. The preparation of the printing plate is as described inExample VII.

A planographic printing plate of equivalent value is obtained if thesolution used for the sensitization of the pre-treated aluminum foilcontains, instead of 0.14 part by weight of the condensation productspecified above, 0.16 part by weight of a condensation product preparedfrom diphenylamine-4-diazonium chloride and formaldehyde in 66 percenthydrobromic acid and precipitated in the form of the bromide or 0.11part by weight of a product prepared from diphenylamine-4-diazoniumchlo- 8 ride and formaldehyde by condensation in 40 percent bydrofluoricacid.

The condensation product is prepared as follows:

Condensation in hydrochloric acid: 46 parts by weight ofdiphenylamine-4diazonium chloride and 6 parts by weight ofparaformaldehyde are stirred in 200 parts by volume of concentratedhydrochloric acid for eight hours at 50 C. and then for twelve hours atroom temperature. The mixture is evaporated in vacuo to dryness at abath temperature of 50 to 55 C. The residue consists of a mixture of theneutral and the acid chloride of the condensation product.

Condensation in hydrobromic acid: 138 parts by weight ofdiphenylamine-4-diazonium chloride, 18 parts by weight ofparaformaldehyde and 300 parts by volume of 66% hydrobromic acid aremixed together and heated for seven hours to 50 C. The mixture is thenevaporated in vacuo at a maximum temperature of 70 C. to dryness. Thecondensation product is obtained in the form of the acid bromide.

Condensation in hydrofluoric acid: 23: 15 parts by weight ofdiphenylamine-4-diazonium chloride, 3.3 parts by weight ofparaformaldehyde and 50 parts by volume of 40% hydrofluoric acid aremixed together and the mixture is heated for 20 hours to 40 C. and for16 hours at 50 C. The solution is evaporated at 50 C. by passing acurrent of air through it and it is completely dried in vacuo overpotassium hydroxide. A product which contains one fluorine ion and onechlorine ion to each diazonium group is obtained.

Example XIII A foil of virgin aluminum sheet is immersed for 30 secondat 70 to C. in a 0.1% solution of polyvinyl phosphonic acid. The foil isrinsed with water and dried and then coated with a solution consistingof 0.1 part by weight of a condensation product prepared fromdiphenylamine-4-diazonium chloride and formaldehyde in phosphoric acidand precipitated in the form of the chloride in 100 parts by volume ofglycol monoethyl ether. The printing plate is prepared as described inExample VII.

The condensation product is prepared as follows:

3.3 parts by weight of paraformaldehyde and 23 parts by weight ofdiphenylamine-4-diazonium chloride are mixed into 56.5 parts by weightof 85% phosphoric acid, with stirring. Condensation is brought about byheating the mixture for 24 hours to 40 C. and then diluting with 320parts by volume of methanol. With constant agitation, 50 parts by weightof calcium carbonate are added gradually to the reaction mixture untilthe pH value of the mixture is about 6. The inorganic salts that arethen formed are filtered off by means of a suction filter and thefiltrate is evaporated to dryness.

Example XIV A thin strip of sheet aluminum is drawn through a bathcontaining a 1 percent solution of polyvinyl phosphonic acid in water at80 to C. Subsequently, the aluminum sheet is rinsed with water, dried,and coated with a light sensitive solution containing 0.5 part by weightof the phosphoric acid condensate of paraformaldehyde and4-methyl-diphenylamine-4-diazonium sulfate described below in 99.5 partsby weight of ethyleneglycol monoethylether.

A printing plate is prepared as described in Example VII.

The phosphoric acid condensationproduct used for sensitizing thesolution is prepared as follows:

In 12 parts by volume of 97 percent phosphoric acid are dissolved 3parts by weight of a condensation product prepared by condensing 20parts by weight of 4'- methyl-diphenylamine-4-diazonium sulfate with1.96 parts by weight of paraformaldehyde in 42 parts by volume of 78percent sulfuric acid and obtained in the form of the chloride. A streamof dry air is passed through the reaction mixture at a temperature of 40C., until the mixture is free from chlorine ions. The mixture is thendiluted with 32 parts by volume of methanol and poured into 250 parts byvolume of isopropanol. The -precipitate which forms is drawn off, washedwith isopropanol and acetone, and dried under vacuum.

Similar results are obtained if an aluminum sheet pretreated as above iscoated with a solution which contains, instead of the condensationproduct mentioned above, a product which was prepared by condensation ofparaformaldehyde with 3-methyl-diphenylamine-4-diazonium chloride,3-ethoxy-diphenylamine-4-diazonium chloride, 2 methoxy diphenylamine 4diazonium chloride, or 2-methoxy-diphenylamine-4-diazonium chloride andconverted into the solid acid phosphate.

Example XV A thin strip of sheet aluminum is drawn through a bath whichcontains a 0.1 percent solution of polyvinyl phosphoric acid inethyleneglycol monomethylether at a temperature of 40 C. Subsequently,the aluminum sheet is dried and coated with a light sensitive solutioncontaining 0.1 part by weight of the chloride of a condensation productof paraformaldehyde and 4-methyldiphenylamine-4-diazonium sulfatedescribed below in 99.9 parts by weight of ethyleneglycolmonomethylether.

A printing plate is prepared as described in Example VII.

The chloride of a condensation product used in the sensitizing solutionis prepared as follows:

Over a period of minutes, parts by weight of4-methyl-diphenylamine-4-diazonium sulfate are introduced into asolution of 1.96 parts by weight of paraformaldehyde in 42 parts byvolume of 78 percent sulfuric acid. The condensation mixture isagitated, first for one hour at room temperature and then for 90 minutesat a temperature of 40 C., and is then left standing overnight at roomtemperature. Subsequently, it is diluted with 150 parts by volume ofwater and a saturated barium chloride solution is added until neither anexcess of barium nor sulfate ions can be detected. After removal of thebarium sulfate, the solution is evaporated to dryness under vacuum attemperatures up to 60 C.

What is claimed is:

1. A method for improving the receptivity for adhesively appliedcoatings of an aluminum surface which comprises treating the surfacewith a solution comprising at least one compound selected from the groupconsisting of an organic phosphonic acid and the esters and saltsthereof, and drying.

2. A method according to claim 1 in which the solution has aconcentration of about 0.001 to 10 percent by Weight.

3. A method according to claim 1 in which the solution also contains ahydrophilic colloid.

4. A method according to claim 1 in which the phosphonic acid ispolyvinyl phosphonic acid.

5. A method according to claim 1 in which the phosphonic acid isS-nitronaphthalene phosphonic acid.

6. A method according to claim 1 in which the phosphonic acid is vinylphosphonic acid.

7. A presensitized printing plate comprising an aluminum base, a firstlayer comprising at least one compound selected from the groupconsisting of an organic phosphonic acid and the esters and saltsthereof, and a second reproduction layer on the first layer.

8. A presensitized printing plate according to claim 7 in which thereproduction layer is light sensitive.

9. A presensitized printing plate according to claim 7 in which thereproduction layer is heat sensitive,

10. A presensitized printing plate according to claim 7 in which thefirst layer also contains a hydrophilic colloid.

11. A presensitized printing plate according to claim 7 in which thephosphonic acid is polyvinyl phosphonic acid.

12. A presensitized printing plate according to claim 7 in which thephosphinic acid is S-nitronaphthalene phosphonic acid.

13. A presensitized printing plate according to claim 7 in which thephosphonic acid is vinyl phosphonic acid.

14. A presensitized printing plate according to claim 7 in which thephosphonic acid is 2-phosphonoethane-lsulfonic acid.

15. A presensitized printing plate according to claim 7 in which thephosphonic acid is vinyl phosphonic acid monomethyl ester.

16. A presensitized printing plate according to claim 7 in which thephosphonic acid is vinyl phosphonic acid monoethyl ester.

17. A presensitized printing plate according to claim 7 in which thereproduction layer comprises a condensation product of4-diazodiphenylamine and formaldehyde.

18. A presensitized printing plate according to claim 7 in which thereproduction layer comprises a benzoquinone diazide.

19. A presensitized printing plate according to claim 7 in which thereproduction layer comprises 4-diazodiphenylamine chloride.

20. A presensitized printing plate according to claim 7 in which thereproduction layer comprises a naphthoquinone diazide sulfonic acidester.

21. A presensitized printing plate according to claim 7 in which thereproduction layer comprises a thiazolidon.

22. A process for making a printing plate which comprises exposing acoated aluminum base material to radiation under a master, the coatingcomprising a first layer comprising at least one compound selected fromthe group consisting of an organic phosphonic acid and the esters andsalts thereof and a second reproduction layer on the first layer, anddeveloping the resulting image, whereby the coating is removed from thebase material in the imagefree areas thereof.

23. A process according to claim 22 in which the radiation is light.

24. A process according to claim 22 in which the radiation is heat.

25. A process according to claim 22 in which the first layer also ahydrophilic colloid.

26. A process according to claim 22 in which the phosphonic acid ispolyvinyl phosphonic acid.

27. A process according to claim 22 in which the phosphonic acid isS-nitronaphthalene phosphonic acid.

28. A process according to claim 22 in which the phosphonic acid isvinyl phosphonic acid.

29. A process according to claim 22 in which the phosphonic acid isZ-phosphonoethane-l-sulfonic acid.

30. A process according to claim 22 in which the phosphonic acid isvinyl phosphonic acid monomethyl ester.

31. A process according to claim 22 in which the phosphonic acid isvinyl phosphonic acid monoethyl ester.

32. A process according to claim 22 in which the reproduction layercomprises a condensation product of 4- diazo-diphenylamine andformaldehyde.

33. A process according to claim 22 in which the reproduction layercomprises a benzoquinone diazide.

34. A process according to claim 22 in which the reprcpduction layercomprises 4diazodiphenylamine chlo- I'l e.

35. A process according to claim 22 in which the reproduction layercomprises a naphthoquinone diazide sulfonic acid ester.

36. A process according to claim 22 in which the reproduction layercomprises a thiazolidon.

37. A presensitized printing plate according to claim 7 in which thereproduction layer comprises a condensation product of3-methoxy-diphenylamine-4-diazonium chloride and formaldehyde.

38. A process according to claim 22 in which the re- References Cited bythe Examiner UNITED STATES PATENTS 2,641,551 6/1953 Smith et a1.2,725,310 11/1955 McBride 117-75 12 Lowell. Cohn 9686 X Gumbinner 9686 XDowdall et al 9675 NORMAN G. TORCHIN, Primary Examiner.

HAROLD N. BURSTEIN, Examiner.

1. A METHOD OF IMPROVING THE RECEPTIVITY FOR ADHESIVELY APPLIED COATINGSOF AN ALUMNIUM SURFACE WHICH COMPRISES TREATING THE SURFACE WITH ASOLUTION COMPRISING AT LEAST ONE COMPOUND SELECTED FROM THE GROUPCONSISTING OF AN ORGANIC PHOSPHONIC ACID AND THE ESTERS AND SALTSTHEREOF, AND DRYING.
 7. A PRESENSITIZED PRINTING PLATE COMPRISING ANALUMINUM BASE, A FIRST LAYER COMPRISING AT LEAST ONE COMPOUND SELECTEDFROM THE GROUP CONSISTING OF AN ORGANIC PHOSPHONIC ACID AND THE ESTERSAND SALTS THEREOF, AND A SECOND REPRODUCTION LAYER ON THE FIRST LAYER.